An analytic study of applying miller cycle to reduce nox emission from petrol engine

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1 An nlytic study of pplying miller cycle to reduce nox emission from petrol engine Yodong Wng, Lin Lin, Antony P. Roskilly, Shengchuo Zeng, Jincheng Hung, Yunxin He, Xiodong Hung, Huiln Hung, Hiyn Wei, Shngping Li, et l. To cite this version: Yodong Wng, Lin Lin, Antony P. Roskilly, Shengchuo Zeng, Jincheng Hung, et l.. An nlytic study of pplying miller cycle to reduce nox emission from petrol engine. Applied Therml Engineering, Elsevier, 2007, 27 (11-12), pp < /j.pplthermleng >. <hl > HAL Id: hl Submitted on 9 Jul 2010 HAL is multi-disciplinry open ccess rchive for the deposit nd dissemintion of scientific reserch documents, whether they re published or not. The documents my come from teching nd reserch institutions in Frnce or brod, or from public or privte reserch centers. L rchive ouverte pluridisciplinire HAL, est destinée u dépôt et à l diffusion de documents scientifiques de niveu recherche, publiés ou non, émnnt des étblissements d enseignement et de recherche frnçis ou étrngers, des lbortoires publics ou privés.

2 Accepted Mnuscript An nlytic study of pplying miller cycle to reduce nox emission from petrol engine Yodong Wng, Lin Lin, Antony P. Roskilly, Shengchuo Zeng, Jincheng Hung, Yunxin He, Xiodong Hung, Huiln Hung, Hiyn Wei, Shngping Li, J Yng PII: S (07) DOI: /j.pplthermleng Reference: ATE 2070 To pper in: Applied Therml Engineering Received Dte: 5 My 2006 Revised Dte: 2 Jnury 2007 Accepted Dte: 14 Jnury 2007 Plese cite this rticle s: Y. Wng, L. Lin, A.P. Roskilly, S. Zeng, J. Hung, Y. He, X. Hung, H. Hung, H. Wei, S. Li, J. Yng, An nlytic study of pplying miller cycle to reduce nox emission from petrol engine, Applied Therml Engineering (2006), doi: /j.pplthermleng This is PDF file of n unedited mnuscript tht hs been ccepted for publiction. As service to our customers we re providing this erly version of the mnuscript. The mnuscript will undergo copyediting, typesetting, nd review of the resulting proof before it is published in its finl form. Plese note tht during the production process errors my be discovered which could ffect the content, nd ll legl disclimers tht pply to the journl pertin.

3 An Anlytic Study of Applying Miller Cycle to reduce NOx Emission from Petrol Engine Yodong Wng *,, b, Lin Lin c, Antony P. Roskilly, Shengchuo Zeng b, Jincheng Hung b, Yunxin He b, Xiodong Hung b, Huiln Hung b, Hiyn Wei b, Shngping Li d, J Yng e School of Mrine Science nd Technology, Newcstle University, Newcstle upon Tyne, NE1 7RU, United Kingdom b Mechnicl Engineering College, Gungxi University, Nnning, Gungxi, , Chin c Nnning College for Voctionl Technology, Nnning, Gungxi, , Chin d Gungxi University of Technology, Liuzhou, , Chin e Mechnicl Engineering College, University of Science nd Technology Beijing, Beijing, Chin Abstrct An nlytic investigtion of pplying Miller cycle to reduce nitrogen oxides (NOx) emissions from petrol engine is crried out. The Miller cycle used in the investigtion is Lte Intke Vlve Closing version. A detiled thermodynmic nlysis of the cycle is presented. A comprison of the chrcters of Miller cycle with Otto cycle is presented. From the results of thermodynmic nlyses, it cn be seen tht the ppliction of Miller cycle is ble to reduce the compression pressure nd temperture in the cylinder t the end of compression stroke. Therefore, it lowers down the combustion temperture nd NOx formtion in engine cylinder. These results in lower exhust temperture nd less NOx emissions compred with tht of Otto cycle. The nlytic results lso show tht Miller cycle rtio is min fctor to influence the combustion temperture, nd then the NOx emissions nd the exhust temperture. The results from the nlytic study re used to nlyse nd to compre 1 *Corresponding uthor: Dr Yodong Wng, Tel: ; Fx: Emil: yodongwng2000@yhoo.com, y.d.wng@ncl.c.uk

4 with the previous experimentl results. An empiricl formul from the previous experimentl results tht showed the reltion of NOx emissions with the exhust temperture t different engine speed is presented. The results from the study showed tht the ppliction of Miller cycle my reduce NOx emissions from petrol engine. Key words: Petrol engine, Miller cycle, NOx emissions, nlytic study Nottions C v Specific het vlue t constnt volume (kj/kg K) C p Specific het vlue t constnt pressure (kj/kg K) cps i k m P Cycles per second Number of the cylinders Specific het rtio Gs mss in the piston-cylinder Pressure in the cylinder (kp) P tm Ambient pressure (kp) P e Pi q in q out Engine brke power (kw) Indicted power of engine (kw) Het input to the engine (kj/kg) Het rejected from the engine (kj/kg) R Gs constnt (R = kj/kg K) r M T Miller Cycle Rtio Temperture in the cylinder (K) T tm Ambient temperture (K) T exh Exhust temperture (K) u Internl energy (kj/kg) V Volume of cylinder (m 3 ) V 0 Clernce volume (m 3 ) V c Swept volume of Otto cycle (m 3 ) 2

5 V c Swept volume of Miller cycle (m 3 ) W Net cycle work (kj/kg) Y NOx NOx emission quntity (ppm) Compression rtio M Compression rtio of Miller Cycle. It is the rtio of the cylinder volume between the piston nd cylinder hed before nd fter n effective compression stroke. The stroke is from the moment tht the intke vlve is closed to the top ded centre (TDC), which is shorter thn tht of Otto cycle. e Expnsion rtio of Miller Cycle. It is the rtio of the cylinder volume between the cylinder hed nd piston before nd fter n effective expnsion stroke. It strts from the TDC to the BDC (bottom ded centre). It is equl to tht of Otto cycle. b th tfa Engine brke therml efficiency: Cycle therml efficiency of engine Engine fuel-ir-cycle efficiency Subscripts 0, 1, 2, 3, 4, 5, - different points of Otto cycle 1, 2, 3, 4, 5, - different points of Miller cycle 1. Introduction In the lst severl decdes since 1960 s, the environmentl problems cused by the humn ctivities hve been seen, such s globl wrming nd worse ir pollutions. This trend hs roused the public wreness to protect the environment on the erth. This hs spred in to ll sectors of life with new legisltion s being formed s result. The engine industry hs tken series of mesures to improve the engine emissions nd to comply with the continued restrictions on the qulity nd quntity of emissions. The need to comply with emissions legisltion mens tht it is lwys pproprite to 3

6 investigte wys of reducing emissions without compromising engine efficiency nd incresing the costs of mnufcturing of engines. The emissions from petrol engines minly re: hydrocrbon (HC), crbon monoxide (CO), crbon dioxide (CO 2 ) nd nitrogen oxides (NOx). Among them, NOx is the most hrmful emissions. It contributes to the formtion of Ozone (O 3 ), nd other irritting smog components, which cuse the urbn summer eye nd nose, etc. The formtion of NOx in engines, re gretly influenced by the following fctors. First of ll, the combustion flme temperture; secondly, the durtion of high temperture, nd thirdly, the oxygen content in the flmes. Among these fctors, flme temperture is the key fctor. The higher of combustion temperture of flme in the engine is, the higher NOx emission will be. In order to reduce NOx emissions from engines, currently there re two min wys: one is fter-tretment tht uses ctlysts to rect with the NOx emitted from the engines; nother is in-cylinder tretment tht reduces the formtion of NOx in the cylinders of engines. For the first method, it reduces NOx emissions effectively, but it increses the cost of the engine mnufcturers nd then customers for the converter nd ctlysts, nd the dditionl spce required for fixing the converter on vehicles. Consequently, the ims to pply in-cylinder tretment mesure re lwys pursued. Miller Cycle ws first proposed by R H Miller In 1947[1]. The proposl ws the use of erly intke vlve closing (EIVC) to provide internl cooling before compression so s to reduce compression work. Miller further proposed incresing the intke 4

7 pressure to compenste for the reduced chrge due to the erly intke vlve closing [2]. The Miller Cycle is cold cycle which hs llowed in the pst n increse in engine performnce with n uprising of the knocking threshold. At this time, Miller Cycle focused on improving the therml efficiency of engine [3 9]. Since Miller cycle is cold cycle, mking use of this chrcteristic of Miller cycle to chieve lower combustion temperture my result in lower NOx formtion in engine cylinder nd then lower NOx emissions. A previous experimentl study for the ppliction of Miller cycle to reduce NOx emissions hs shown the effect of the reduction of NOx emissions [10]. But thermodynmic investigtion hs not been crried out yet. The im of this study is to continue the investigtion on the bse of the experimentl results, to crry out thermodynmic nlysis of the ppliction of Miller cycle on petrol engine to reduce NOx emissions. 2. The Concept of Miller Cycle 2.1 The bsic chrcteristic of Miller Cycle The chrcteristic of Miller cycle is: The effective compression stroke of engine is shorter thn the expnsion stroke. Fig 1 illustrtes the comprison of stndrd Otto cycle to Miller cycle; the P-V digrms re lso shown in the figure. Assuming the pressure in cylinder t the strting point 0 is P 0, the volume is V 0, the swept volume of cylinder for Otto Cycle is V c, for Miller Cycle is V c. 5

8 For Otto cycle, shown in Fig 1 (), the work process is: intke stroke 0 1, compression stroke 1-2, combustion nd expnsion stroke 2-3-4, nd exhust stroke 4-1-0, where the compression rtio is identicl to the expnsion rtio, higher expnsion rtio cuses higher compression rtio nd results in hrmful engine knocking while the compression rtio excesses 10 ~ 12. For Miller cycle s shown in Fig.1 (b), however, llows the compression nd expnsion rtios to be preset independently. The work process is: intke stroke 0-1-1; then n dditionl intke blow bck process 1-1, which is the min difference between Miller cycle to Otto cycle; compression stroke 1-2; combustion nd expnsion stroke ; exhust stroke From the P-V digrm of Miller cycle, higher engine efficiency is expected with incresed expnsion rtio, while engine knocking cn be voided by reducing the effective compression rtio. 2.2 The bsic mechnism of Miller Cycle to reduce NOx emissions As mentioned bove, the min cuse of NOx formtion is the combustion flme temperture in the cylinder during the combustion process. Utilizing the chrcteristic of Miller cycle, to reduce the compression pressure nd the compression temperture t the end of compression stroke (t the point 2 in P-V digrm), therefore to chieve lower combustion temperture t the end of combustion process (point 3 in P-V digrm), then lower NOx formtion nd emissions my be expected. This is the thermodynmic bsis of pplying Miller cycle to reduce NOx emission from petrol engines. 6

9 Fig 2 illustrtes the P-V digrm of this concept of Miller cycle. Cycle is the stndrd Otto cycle. Cycle is the Miller cycle. The intke vlve keeps open (closes lter thn Otto cycle) during portion of compression stroke. Some of the intke ir into cylinder is rejected into the intke pipe. Then the mount of intke ir into cylinder is reltively less thn Otto cycle nd this reduces the effective compression rtio. At the end of the compression stroke, the pressure nd temperture in cylinder re lower thn those of stndrd Otto cycle; nd then during the combustion stroke, the combustion temperture is then lower, this my result in less NOx formtion in the cylinder; finlly, in the exhust stroke it leds to less NOx emissions. 2.3 The methods to relize Miller Cycle There re three min methods to relize Miller Cycle [5 8]: () Using rotting vlve between the intke pipe nd intke vlve on cylinder hed to control the quntity of intke ir Erly Rotry-Vlve Closing (ERVC); (b) Closing the intke vlve before the termintion of the intke stroke Erly Intke Vlve Closing (EIVC); (c) Keeping intke vlve open during portion of the compression stroke, thus rejecting prt of the chrge nd reducing the net compression rtio Lte Intke- Vlve Closing (LIVC - s shown in Fig 2). This version of LIVC Miller cycle is pplied to the investigtion. A schemtic vlve timing digrm of LIVC Miller cycle is shown in Fig Experimentl results from previous engine tests 7

10 Experimentl studies to investigte nd to compre the performnce nd emission chrcteristics of the originl engine (Otto cycle) to those of Miller cycle hve been crried out. The detil results re presented in the previous published pper by the uthor [10]. The engine used for the experimentl tests is Rover K series 16-vlve twin-cmshft petrol engine, type K TBI, mde by the Rover Group Ltd in It hs 1397 cm 3 displcement, compression rtio 9.5, mximum power 70.8 kw (95 hp) /6250 rev/min (torque 106.7Nm), mximum torque 124 Nm /4000rev/min, equipped for Rover 200 &400 series crs. The schemtic digrm of the test rig is showed in Fig 4. For the experimentl study, two versions of LIVC Miller cycle were designed, relized nd tested in the tests: Miller cycle 1, intke vlve closed 15 degrees lter thn tht of originl Otto cycle, the Miller cycle rtio is Miller cycle 2, intke vlve closed 30 degrees lter thn tht of originl Otto cycle, the Miller cycle rtio is Figure 5 nd Fig 6 show the test results of exhust temperture nd NOx emissions of the petrol engine t three different cycles on different engine speed nd lod. Fig 5 presents the comprison of the exhust tempertures t the outlet of exhust mnifold. The results showed tht the exhust tempertures of Miller cycles t different engine speed were ll lower thn tht of stndrd Otto cycle. For Miller cycle 1, the temperture differences were between 20 ºC to 62 ºC, compred with those of Otto Cycle. The mximum temperture difference ws 11%. For Miller cycle 2, compred with Otto cycle, the temperture differences were between 45 ºC to 112 ºC. The mximum temperture difference ws 19%. Fig 6 shows the test results of NOx 8

11 emissions nd the comprison of different cycles. For the cycles tested, the NOx emissions of Otto cycle were the highest one, from 620 ppm to 2610 ppm. For Miller Cycle 1, the NOx emissions were less thn tht of Otto cycle, the reductions were from 130 ppm to 665 ppm. The mximum difference ws 51%. For Miller cycle 2, the NOx emissions were much less thn Otto cycle, the reductions were from 360 ppm to 850 ppm; the mximum difference ws 58%. From the experimentl results bove, the reltion of engine exhust temperture versus NOx emissions t different engine speed; the reltion of engine exhust temperture versus Miller cycle rtio; nd reltion of engine NOx emissions versus Miller cycle rtio re found, which re showed in the following figures. Fig 7 presents the reltion of engine exhust tempertures versus NOx emissions t different engine speed. The results show tht when the exhust tempertures were low, the NOx emissions were low; when the exhust tempertures were higher, the NOx emissions were higher when the engine run t the sme speed. Fig 8 () shows the reltion of exhust gs temperture versus Miller cycle rtio t the engine full lod. Fig 8 (b) presents the reltion of NOx emission versus Miller cycle rtio. For Otto cycle, Miller cycle rtio ws 1; exhust gs temperture ws 808 ºC; the relevnt NOx emission ws 2610 ppm. For Miller cycle 1, the Miller cycle rtio ws 0.95, exhust gs temperture ws 788 ºC, the relevnt NOx emission ws 2400 ppm. For Miller cycle 2, the Miller cycle rtio ws 0.90, exhust gs temperture ws 752 ºC, the relevnt NOx emission ws 1420 ppm. This shows tht the lower of exhust temperture is, the less of the NOx emission is, t the sme engine speed. 9

12 Fig 8 (c) shows the reltion of engine therml efficiency versus the Miller cycle rtio. It cn be seen tht the engine therml efficiency incresed when the Miller cycle rtio lowered down. In contrst, for the engine power output, it ws reduced when the Miller cycle rtio of the engine dropped down, s shown in Fig 8 (d). The reson is becuse the intke stroke of Miller cycles is shorter, then ir nd fuel input to the engine cylinder is less, therefore the het energy input to the engine is less. The less het energy input results in the less power output in spite of the increse of the engine therml efficiency. 4. Thermodynmic nlysis of Miller cycle The following is the thermodynmic nlyses of the LIVC version of Miller cycle, compred to tht of Otto cycle. 4.1 Otto cycle As shown in Fig 2, the petrol engine working on the stndrd Otto cycle hs the following process: intke, compression, combustion nd expnsion, nd exhust. The equtions for the cycle clcultion cn be found in litertures [11] nd re not listed here. 4.2 Lte Intke Vlve Closing Miller Cycle 10

13 As lso shown in Fig 2, the petrol engine working on the Lte Intke Vlve Closing Miller cycle hs the following process: Intke stroke, constnt pressure suction process 0 1, P 1 = P 0 = P tm ; T 1 = T 0 = T tm (1) Intke blowbck process 1 1, P 1 = P 1 ; T 1 = T 1 (2) Compression stroke 1 2, isentropic compression process 1 2, P P 2 1 V = V 1 2 k (3) T T V k k 1 = = M 1 V2 ε (4) Where M is the compression rtio of Miller Cycle: V 1 ε M = (5) V2 In order to compre the difference between Miller cycle nd Otto cycle, concept of Miller Cycle Rtio r M [12] is dopted to describe the difference. ε M = r ε (6) M When r M = 1, M =, the Miller cycle is identicl with the Otto cycle. Combustion nd expnsion stroke 2 3 4: Constnt volume het ddition process

14 12 T T P P = (7) ) ( ) ( v in T T c u u q = = (8) Isentropic expnsion process 3 4, k V V P P = (9) = = k e k V V T T ε (10) Where the expnsion rtio of Miller cycle is not the sme s the compression rtio, which is: V V V V e = = ε (11) Exhust stroke 4 1 0: Constnt volume het rejection process 4 1, T P T P = (12) ) ( ) ( T T c u u q v out = = (13) Constnt pressure exhust process 1 0, P 5 = P 1 = P 0 (14) The exhust gs expnds to the tmospheric pressure when the exhust vlve opens, the exhust temperture cn be seen s the gs temperture t the stte 5 (Fig 2), which my be determined from reversible dibtic reltionships s

15 T exh = T 5 = Net cycle work is T 3 P P 5 3 ( k 1) / k (15) W ( u ) m( u ) = m u (16) u1 The engine indicted power Pi (kw) produced by the engine is Pi = m W cps i (17) P V RT 1 1 m = (18) 1 The brke power produced by the engine is: P e = b Pi (19) Cycle therml efficiency: η th = W Q in = ( u3 u4 ) ( u2 u1 ) ( u u ) 3 2 ( T4 T1 ) = 1 (20) ( T T ) For rel engine, its cycle cn be described s kind of fuel-ir-cycle [11], the corresponding efficiency, tfa is: tfa 0.75 th (21) 3 2 The brke thermodynmic efficiency of n ctul engine, b, is roughly 0.8 times tht of the fuel-ir cycle [11], tht is: b 0.80 tfa (22) 5. Results from the thermodynmic nlyses 13

16 A computtion bsed on the bove thermodynmic nlyses is crried out to clculte the engine performnce for Otto cycle nd Miller cycles. The rnges of Miller cycle rtio for the clcultion were selected from 0.9 to 1.0. The clcultion results re presented in Figure 8. As for the clcultion of NOx emissions, Wunning, J.G. [13-14] pointed out tht there re three predominntly mentioned sources of nitric oxides from combustion processes: prompt NO, fuel NO nd therml NO. Whereof the therml NO-formtion, described by the Zeldovich-mechnism is the most relevnt source for the combustion of clen fuels. The NOx formtion is strongly influenced by the combustion tempertures. Becuse of tht strong temperture influence, most NOreducing techniques try to cut off pek tempertures, keep the residence time in high temperture res low, nd void high oxygen concentrtion in these res. Webster, T. found tht there ws liner reltion between the NOx emissions nd flme tempertures in burners [15]: the higher the flme temperture is, the more NOx emissions is. Mncini, M. nd Weber, R. found the similr results s tht of Webster s. They found tht there ws reltion between NOx emissions nd flme temperture [16]: NOx [ppm] = 0.31* T comb. [ºC] Milni, A. nd Sponro, A. found tht the therml NO formtion is extremely sensitive to process temperture nd presented figure showed tht NOx emissions re incresed when the process temperture incresed [17]. In this study, the exhust tempertures were mesured. The exhust temperture is directly relted to the combustion temperture nd is good representtion of the combustion tempertures. Referring to the recommendtion from litertures, by pplying the exponentil fitting to the previous experimentl results t 14

17 different engine speeds n (r/min), empiricl formule of NOx emission versus exhust temperture re drwn, which is (s shown in Fig 7): x2 T Y = x exh (23 ) NOx 1 e Where Y NOx is the NOx emissions (ppm), T exh is the temperture of the exhust gs (ºC). x 1 nd x 2 re coefficients, which re listed in Tble 1. The vlidity rnge of the empiricl correltion ws from 399 to 808 ºC. The relibility of the eqution is shown in the form of the squre of the correltion coefficient (R-squred vlue) in Tble 1. The simultion results of exhust temperture versus the Miller cycle rtio re presented in Fig 8 (). From the figure, it cn be seen tht the exhust temperture is dropped s long s the Miller cycle rtio is reduced. The lower the Miller cycle rtio r M is, the lower the exhust temperture is. While the Miller cycle rtio r M = 1, this is Otto cycle, the exhust temperture T exh equls to 808 ºC; when r M = 0.9, T exh = 730 ºC. Fig 8 (b) shows the simultion results of NOx emissions versus the Miller cycle rtio r M. When the Miller Cycle rtio r M = 1, this is Otto cycle, the NOx emissions rech the highest vlue, 2826 ppm; when r M = 0.9, the NOx emissions re 1600 ppm. The figure shows tht the lower the Miller cycle rtio is, the less the NOx emissions re. Similr results cn be found from the other reserches [9, 16-18]. 15

18 The simultion results of engine therml efficiency versus the Miller cycle rtio re shown in Fig 8 (c). While the Miller cycle rtio r M = 1, this is Otto cycle, the engine therml efficiency b is the lowest vlue, 23.50%, when r M = 0.9, b = 27.40%, which is the highest vlue. This result shows tht Miller cycle cn improve the therml efficiency of engine, which is the originl ide tht Mr Miller to propose the cycle in Similr results cn be found in the other reserches [16 23]. The simultion results of engine power output versus the Miller cycle rtio re presented Fig 8 (d). The figure shows the trend tht the engine power output reduces when the Miller cycle rtio lowers down. When r M = 0.9, P e = kw. While the Miller cycle rtio r M = 1, this is Otto cycle, the engine power output P e is the highest, reches to kw. 6. Conclusions The objective of this study is relized. The results from the thermodynmic nlyses bsed on the previous experimentl results demonstrte tht pplying Miller cycle to petrol engine is ble to reduce NOx emissions. The results from the computtion show tht the Miller cycle rtio is the min fctor to control the combustion temperture, exhust temperture nd then to control the NOx emissions from the petrol engine. The reduction of Miller cycle rtio results in the reduction of the combustion temperture then exhust temperture, nd the reduction of NOx emissions. 16

19 The nlytic results lso show tht the reduction of Miller cycle rtio results in the increse of engine therml efficiency, but it cuses the reduction of engine power output. The results from the thermodynmic nlyses re good explntion for the previously experimentl results. The results my be ble to pply to the other petrol engines for the similr studies. Further work is needed to optimise the effect of Miller cycle such s: A detiled study to select the optimising point of Miller cycle rtio, i.e. optimising the prmeters of the Lte Intke Vlve Timing of the engine, to find the best opertion prmeters for both NOx emission reduction nd the engine power output. Further experimentl nd nlyticl studies re lso necessry to find out the mechnism of Miller cycle to reduce NOx emissions in more detils. Acknowledgements The support of the Fculty of Computing, Engineering nd Technology of Stffordshire University of UK is gretly pprecited, so too is the support of Gungxi University of Chin. References [1] Miller, R. H.; Superchrging nd Internl Cooling Cycle for High Output, Trnsctions of ASME 69, 1947, p

20 [2] Miller, R. H., Lieberherr, H.U.; The Miller Superchrging System for Diesel nd Gs Engines Operting Chrcteristics, CIMAC, 1957, Proceedings of the 4th Interntionl Congress on Combustion Engines, Zurich, Jun 15-22, 1957, p [3] Okmoto, K., Zhng, F.R., Shimogt, S., Shoji, F., Knesk, H. nd Ski H., Study on Miller Cycle Gs Engine for Co-genertion Systems - Effect of Miller Cycle on the Performnce of Gs Engine, SAE Specil Publictions, 1996, Vol. 1171, p [4] Thring, R.H., The Flexible Diesel Engine, Proceedings of the Interntionl Congress nd Exposition, Detroit, USA, 1990, SAE Pper No , SAE Specil Publictions, 1990, p [5] Clrke, D. nd Smith, W. J.; Simultion, implementtion nd nlysis of the Miller cycle using n inlet control rotry vlve, Vrible vlve ctution nd power boost, SAE Specil Publictions, 1997, Vol (SAE Pper No ), pp [6] Shimogt, S., Homm, R., Zhng, F.R., Okmoto, K., Shoji, F.; Study on Miller Cycle Gs Engine for Co-genertion Systems- Numericl Anlysis for Improvement of Efficiency nd Power, SAE Pper No , SAE Specil Publictions, 1997, p [7] Frnc, I.; Miller Cycle - Outline nd Generl Considertions, Diesel Ricerche S.P.A. Technicl report, 1996 [8] Okmoto, K., Zhng, F. R., Morimoto, S., Shoji, F.; Development of Highperformnce Gs Engine Operting t Stoichiometric Condition - Effect of Miller Cycle nd EGR-, Proceedings of CIMAC Congress 1998 Copenhgen, 1998, p

21 [9] Stebler, H., Weisser, G., Horler, H. nd Boulouchos, K.; Reduction of NOx Emissions of D.I. Diesel Engines by Appliction of the Miller-System: An Experimentl nd Numericl Investigtion, SAE Pper No , SAE Specil Publictions, 1996, p [10] Wng Y.D. nd Ruxton, T., An Experimentl Investigtion of NOx Emission Reduction from Automotive Engine Using the Miller Cycle, Proceedings of ICEF2004, ASME Internl Combustion Engine Division, 2004 Fll Technicl Conference, Long Bech, CA, USA, October 24-27, [11] Tylor, C. F. The Internl Combustion Engine in Theory nd Prctice. Vol. 1, nd 2, Second Edition, Cmbridge, MA: M.I.T. Press, [12] Koichi Htmur, Motoo Hykw, Tsuyoshi Goto, Mitsuo Hitomi, A study of the improvement effect of Miller-cycle on men effective pressure limit for highpressure superchrged gsoline engines, JSAE Review 18 (1997) p [13] Wunning, J.G., Flmeless Combustion in the Therml Process Technology, Second Interntionl Seminr on High Temperture Combustion, Stockholm, Sweden, Jn [14] Wunning, J.A. nd Wunning, J.G., Flmeless oxidtion to reduce therml NOformtion, Progress in Energy nd Combustion Science, Vol. 23, p.81 94, [15] Webster, T., Burner Technology for Single Digit NOx Emissions in Boiler Applictions, CIBO NOx Control XIV Conference, Sn Diego, CA, Mrch 13, [16] Kesgin U., Study on prediction of the effects of design nd operting prmeters on NOx emissions from lenburn nturl gs engine, Energy Conversion nd Mngement, Vol. 44, 2003, p [17] Milni, A. nd Sponro, A., DILUTED COMBUSTION TECHNOLOGIES, IFRF Combustion Journl, Article Number , Februry 2001, ISSN X 19

22 [18] Ki-Doo Kim nd Dong-Hun Kim, Improving the NOx-BSFC Trde Off of Turbochrged Lrge Diesel Engine Using Performnce Simultion, Hyundi Hevy Industries Co., Ltd, pdf [19] Kesgin, U., Efficiency improvement nd NOx emission reduction potentils of two-stge turbochrged Miller cycle for sttionry nturl gs engines, Interntionl Journl of Energy Reserch, 2005; vol.29: p [20] Mncini, M. nd Weber, R., Formtion nd destruction of nitrogen oxides in combustion of nturl gs with high temperture ir, Proceedings of the 5th Interntionl Symposium on High Temperture Air Combustion nd Gsifiction (HTACG), Yokohm, Jpn, October [21] Ge, Y., Chen, L., Sun, F., Wu, C., Reciprocting het-engine cycles, Applied Energy, vol. 81, 2005, p [22] Fukuzw,Y., Shimod, H., Kkuhm, Y., Endo, H. nd Tnk, K., Development of High Efficiency Miller Cycle Gs Engine, Mitsubishi Hevy Industries, Ltd. Technicl Review Vol.38 No.3 (Oct. 2001), p [23] Anderson, M., Assnis, D. nd Filipi, Z., First nd Second Lw Anlyses of Nturlly-Aspirted, Miller Cycle, SI Engine with Lte Intke Vlve Closure, SAE Technicl Pper Series , Interntionl Congress nd Exposition Detroit, Michign, Februry 23-26, 1998, p

23 P 3 P P P V 0 V 0 + V c V V 0 V 0+V c V 0+V c V Intke Intke Intke blow Compression Compression Combustion & Expnsion Combustion & Expnsion Exhust Exhust () Otto Cycle (b) Miller Cycle Fig 1 A comprison of stndrd Otto Cycle to Miller Cycle 21

24 P 3 3 Otto cycle 2 2 Miller Cycle 4 P V 0 V 0 + Vc V 22 Fig 2 A comprison of P-V digrm of Otto Cycle to Miller Cycle

25 Miller Cycle ( LIVC ) Otto Cycle Lte Intke-Vlve Closing (LIVC) Fig 3 Schemtics of Vlve Timing of Miller cycle (LIVC) 23

26 PC FUEL TANK AIR BOX OPERATING DATA ACQUISITION EXHAUST EMISSION DYNAMOMETER ENGINE EXHAUST TEMPERATURE Fig 4 Schemtic Digrm of Test Rig Exhust Gs Temperture (ºC) n (rpm) Otto cycle Miller Cycle 1 Miller Cycle 2 Fig 5 Exhust Gs Temperture Comprison of Otto Cycle to Miller cycle 24

27 NOx (ppm) n (rpm) Otto cycle Miller Cycle 1 Miller Cycle 2 Fig 6 NOx Emissions Comprison of Otto Cycle to Miller cycle 25

28 Texh n1: Y NOx1 = e R 2 = NOx emissions (ppm) Texh n2: Y NOx2 = 0.122e R 2 = n3: Y NOx3 = e Texh R 2 = Texh n4: Y NOx4 = e R 2 = Texh n7: Y NOx7 = e R 2 = Texh n5: Y NOx5 = e R 2 = Texh n8: Y NOx8 = e R 2 = Texh n6: Y NOx6 = e R 2 = n1 = 6250 n2 = 5500 n3 = 5000 n4 = 4500 n5 = 4000 n6 = 3500 n7 = 3000 n8 = 2000 n - engine speed (r/min) Texh (ºC) Fig 7 Exhust Temperture Versus NOx Emissions t different engine speed 26

29 900 Exhust Temperture (ºC) Miller Cycle Rtio Experimetl results Simultion results Fig 8 () Experimentl nd simultion results of exhust temperture Versus Miller Cycle Rtio 27

30 NOx Emission YNOx (ppm) rm Y NOx = e R 2 = Miller Cycle Rtio r M Fig 8 (b) Experimentl nd simultion results of NOx emissions Versus Miller Cycle Rtio 30.0 b (%) Miller Cycle Rtio Experimentl results Simultion results Fig 8 (c) Experimentl nd simultion results of Engine Therml efficiency Versus Miller Cycle Rtio 28

31 60.0 Pe (kw) Experimentl results Simultion results Miller Cycle Rtio Fig 8 (d) Experimentl nd simultion results of Engine Power Versus Miller Cycle Rtio 29

32 Tble 1 Coefficient x 1, x 2, nd R-squred vlues Engine speed (r/min) Coefficient x 1 Coefficient x 2 R-squred vlue (R 2 )